Process of manufacturing cathode-ray tubes such as color cathode-ray tubes or monochromatic cathode-ray tubes include a step of joining a panel and a funnel to each other while they are passing through a frit sealing furnace, i.e., joining them to each other with a frit seal. Usually, a frit seal furnace comprises a furnace body having a heating means and a conveyor belt extending through the furnace body. On the conveyor belt, there is placed a mount which supports a tube body composed of a panel and a funnel that are superposed one on the other with a frit glass interposed therebetween. The panel and the funnel are joined to each other with a frit seal when they are fed through the furnace body by the conveyor belt.
Heretofore, the conveyor belt in a frit seal furnace is in the form of a mesh belt combined with a helical coil. In the frit seal furnace, a jet nozzle is attached to the neck to bake an intermediate film (primal film) coated in the step of forming a fluorescent surface, and air if caused to flow upwardly for joining the panel and the funnel with a frit seal while replacing air in the tube body.
The mount for supporting the panel and the funnel comprises a base in the form of a frame, a holder connected to the base by a plurality of legs for engaging a round portion (circular portion at the boundary between the neck and the funnel) of the tube body, and abutments for abutting respectively against three sides of the panel and the funnel
In the conventional frit seal furnace, the mesh belt (conveyor belt) of metal is driven in sliding engagement with metal skid rails which support the mesh belt. Therefore, metal particles are scraped off by sliding frictional engagement between the mesh belt and the metal skid rails. These metal particles fly up because of the upward air streams, and tend to be attached to the frit glass. As a result, the completed cathode-ray tube has a deteriorated pressure resistance at the frit seal region.
During long usage of the frit seal furnace, metal particles produced as described above and glass pieces of broken tube bodies are deposited on the floor of the frit seal furnace. When the deposited metal particles and glass pieces are to be removed, the metal belt is cut off to provide a gap, and the furnace floor is cleaned with a cleaner through the gap while moving the metal belt. Consequently, it is time-consuming to clean the furnace floor.
After the furnace floor has been cleaned up, the metal belt is joined again. However, the restored metal belt contacts a drive drum under a different condition, and is liable to become tortuous. As it takes considerable time to make adjustments for reducing such a tortuous condition of the metal belt, the initial process of starting to operate the frit seal furnace is delayed.
In view of the aforesaid drawbacks of the prior art, it is an object of the present invention to provide a frit seal furnace which is capable of suppressing the production of metal particles that would adversely affect the pressure resistance of the frit seal region of a cathode-ray tube, and also of improving the process of cleaning a furnace floor and reducing a tortuous condition of a conveyor belt.
Another object of the present invention is to provide a mount for supporting a cathode-ray tube in such a frit seal furnace.